Marine Interpretation Message
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948
AGPN40 KWNM 230936
MIMPAC

Marine Weather Discussion for N Pacific Ocean
NWS Ocean Prediction Center Washington DC
136 AM PST Thu Nov 23 2017

.FORECAST DISCUSSION...Major features/winds/seas/significant
.weather for the North Pacific N of 30N and E of 150W.

Gale force winds slated for Saturday will be retained because a
series of troughs and fronts will pass east across the northern
waters. Satellite images show most of the cold cloud across the
northern and central waters. At 06Z, NCEP map has a cold front
across the northern waters that extends from low pressure 992 MB
over Vancouver Island and a trough trough extends southwest from
the same low. High pressure 1022 MB over the southern waters
has extended  its ridge into the southeaster portion of the
central waters and southern waters. Pressure gradient over the
central and southern waters is fairly relaxed while over the
northern waters, pressure gradient is fairly tight where maximum
winds now just below gale force threshold have been observed.
Though winds are now diminishing as a trough moves across the
northern waters it will be quickly followed by a cols front that
will re-enforce the gradient and allow winds to reach gale force
strength again. Models GFS/CMC/ECMWFHR/UKMETHR/NAM/NOGAPS/JMA
have initialized the 06Z surface observations fairly well with
just small variations mostly on the actual position of the cold
front and trough to the west of the region. The models are
generally in good agreement in the short term on building high
pressure over the southern waters and as low pressure approaches
the waters form the gulf of Alaska, models agree on tightening
the pressure gradient again over the northern waters and allow
winds to increase. In the extended period, models show some
differences on the position of low pressure that will approach
from the southwest with GFS being the fastest and UKMETHR being
the slowest keeping ECMWFHR and CMC in between. GFS brings the
low into the northern waters while UKMETHR and ECMWFHR keeps it
over the western edge of the northern waters while CMC weakens it
and keeps it west of the northern waters. Otherwise, models have
a very similar solution apart from timing and track differences.
ECMWFHR is the only model that keeps the winds below gale force.
So either model choice will need some adjustments in the
extended period. For now will retain the official winds.

.SEAS...peaked at 18 ft over the northeastern portion of the northern
waters and they are relatively high over the rest of the
northern and central waters. Seas are less than 6 ft over the
southern waters south of 35N. Both wave models NWW3 and ECMWFWAVE
fit the observed seas pattern well but have differences on the
actual peak value over the northern waters where NWW3 has a peak
at 18 ft while ECMWFWAVE peak value is 16 ft. For this issuance
will continue with NWW3 initially then switch to ECMWFWAVE in the
extended period.



.EXTRATROPICAL STORM SURGE GUIDANCE...


.WARNINGS...Preliminary.

.PZ5 Washington/Oregon Waters...
.PZZ800...Inner Waters from Cape Flattery to Cape Shoalwater...
     Gale Possible Saturday night into Monday.
.PZZ900...Outer Waters from Cape Flattery to Cape Shoalwater...
     Gale Possible Saturday night into Monday.
.PZZ805...Inner Waters from Cape Shoalwater to Cape Lookout...
     Gale Possible Saturday into Saturday night.
     Gale Possible Sunday night into Monday.
.PZZ905...Outer Waters from Cape Shoalwater to Cape Lookout...
     Gale Possible Saturday into Monday.
.PZZ810...Inner Waters from Cape Lookout to Florence OR...
     Gale Possible Saturday into Sunday.
.PZZ910...Outer Waters from Cape Lookout to Florence OR...
     Gale Possible Saturday into Sunday.
.PZZ815...Inner Waters from Florence OR to Point St. George...
     Gale Possible Saturday into Sunday night.
.PZZ915...Outer Waters from Florence OR to Point St. George...
     Gale Possible Saturday into Sunday night.

.PZ6 California Waters...
.PZZ820...Inner Waters from Point St. George to Point Arena...
     Gale Possible Saturday night.
     Gale Possible Sunday night.
.PZZ920...Outer Waters from Point St. George to Point Arena...
     Gale Possible Saturday into Sunday night.
.PZZ925...Outer Waters from Point Arena to Pigeon Point...
     Gale Possible Saturday.
     Gale Possible Sunday.
.PZZ840...Inner Waters from Santa Cruz Island, CA to San Clemente Island, CA...
     Gale Possible Monday night.

$$

.Forecaster Musonda. Ocean Prediction Center.



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